The present invention relates to high efficiency air filtration systems, and more particularly to a system of suspended, mutually sealed filter units forming all or part of the ceiling or overhead boundary of a space into which filtered air is introduced by downward, laminar flow.
In locations requiring air substantially free of all foreign matter, such as for certain industrial process, pharmaceutical and medical applications, etc. it is a common practise to provide a plurality of filter units, comprising a core of pleated media sealed to a surrounding, box-like frame, resting upon or suspended from support structure to form all or a portion of the top of an enclosed space. Incoming air is distributed over the upstream sides of the filter units and flows downwardly through the media to the room or space. Each filter unit is sealed about its periphery to insure that only air which has passed through the high efficiency filter media reaches the room or space, commonly known as a "clean room", "clean tunnel" or "clean bench."
A number of means have previously been employed for preventing air leaks around or through the framing system which supports the filter units, or between the filter units and frame. Such means have included the use of mastic sealants at all seams and joints of the framing members, as well as gaskets between adjacent surfaces of the filter units and framing members. Other means directed to this purpose include framing systems wherein a latticework of upwardly directed, U-shaped channels contain a liquid wherein edge portions on each side of the filter units are disposed to provide a liquid seal about the filter units, such as disclosed in U.S. Pat. No. 3,486,311.
Another consideration in the design of overhead air filtration systems is the manner in which the individual filter units are installed upon the support structure. According to an installation system which has been widely used for some time, a gridwork of inverted T-bars is suspended from overhead structure to provide openings wherein the filter units are placed. In order to install an individual unit, it must be lifted endwise through the opening in the gridwork and then lowered onto the support structure. This requires considerable clearance between the gridwork and the overhead structure from which it is suspended, in addition to the inconvenience of physically lifting the entire filter unit through the opening to a position entirely above the support structure before being lowered into place.
It is a principal object of the present invention to provide a high efficiency air filtration system forming all or a part of the ceiling of a "clean room," or the like, having novel and improved sealing means to prevent air leaks around the individual filter units.
Another object is to provide a unique and improved downflow air filtration system wherein there is no leakage of unfiltered air around the individual filter units, although the latter are not required to be sealed in air tight engagement with the framing members by which they are supported.
A further object is to provide air filter units wherein a conventional filter core of pleated, high efficiency media is surrounded by a metal frame of unique construction permitting suspension of the units in side-by-side relation from a gridwork of tracks and the sealing of adjacent units to one another rather than to the support structure.
Still another object is to provide an air filter construction and support structure therefor in a downflow filter installation which permit the filter units to be positioned and installed in a simple and rapid manner.
A still further object is to provide a downflow air filter unit which may be installed with minimal vertical clearance above the structure by which the filter unit is supported.
Other objects will in part be obvious and will in part appear hereinafter.